D3: CarrierStore + LoadPortStore

Per-CARRIERID and per-PORTID stores wrap the D1 FSMs, mirroring the
ProcessJobStore / ExceptionStore pattern: heap-allocated state machines
keyed in a std::map, non-movable to keep this-capture lambdas safe,
synthetic create() that wires per-row change handlers into the store's
top-level callbacks.

CarrierStore:
  create(carrierid, port_id, capacity)  — default 25-slot map
  fire_id_event / fire_slot_map_event / fire_access_event
  set_id_handler / set_slot_map_handler / set_access_handler

LoadPortStore:
  create(port_id)
  associate(pid, carrierid) / disassociate(pid)
  fire_transfer_event / fire_reservation_event
  set_transfer_handler / set_reservation_handler / set_association_handler

Both join EquipmentDataModel alongside process_jobs / control_jobs /
exceptions.  Six test cases cover create-dedup, ID-status change
observation, slot-map / access independence, port association,
transfer lifecycle, and reservation handler firing.

Server-side dispatch (S3F17 -> CarrierStore::fire_id_event, S3F25 ->
LoadPortStore transfer) lands in D4.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

include/secsgem/gem/data_model.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "secsgem/gem/store/alarms.hpp"
+#include "secsgem/gem/store/carriers.hpp"
 #include "secsgem/gem/store/clock.hpp"
 #include "secsgem/gem/store/control_jobs.hpp"
 #include "secsgem/gem/store/equipment_constants.hpp"
@@ -36,6 +37,8 @@ struct EquipmentDataModel {
   ProcessJobStore           process_jobs;
   ControlJobStore           control_jobs;
   ExceptionStore            exceptions;
+  CarrierStore              carriers;
+  LoadPortStore             load_ports;
 
   // Convenience: VID -> value lookup spanning SVIDs and DVIDs.
   std::optional<s2::Item> vid_value(uint32_t vid) const {